Specific Cancer Problem Under Study: The High Rate of Negative Breast Biopsies. Mammography is recognized today as the best diagnostic examination for the detection of breast cancer and breast calcifications are an important radiographic sign. In early breast cancer the calcifications are often the only diagnostic marker. Problem: Radiologists often find it difficult to distinguish between benign and malignant calcifications from mammograms and the result is a very high degree of negative biopsies. Cancer Control Hypothesis: A recently conducted blind study in this laboratory has shown that equivocal calcifications seen on mammograms can often be easily and correctly diagnosed from radiographs of excised breast tissue when the images are viewed under high magnification. Fifteen patterns have been identified as being pathognomonic. Hypothesis:-there must be an underlying reason why benign calcifications are radiographically different from malignant calcifications; the reason is that they contain different elements or different proportions of the same elements. Cancer Control Intervention: Unless new methods are found to accurately diagnose malignant and benign breast calcifications, the high rate of negative biopsies will persist. One solution would be development of contrast agents with differential affinity for benign and malignant calcifications. Such agents would not only make the calcifications more discernable but could also provide the means for visualizing the microcalcifications associated with very early breast cancer. The target population for the contrast agents would be women whose mammograms are equivocal based on calcifications. Follow-up mammograms using contrast would be obtained. Calcifications would be more visible; the result would be fewer negative biopsies. Symptomatic women with dense breasts would be candidates for contrast enhancement before mammography. Cancer Control Research Phase: A rational basis for the development of such contrast agents is knowledge of the chemical elements in the calcifications. The purpose of this study is to determine the elemental composition of breast calcifications. Analysis will be done on surgical breast specimens from 50 cases using scanning electron microscopy, energy dispersive spectroscopy, x-ray mapping, and photomicroscopy employing techniques developed in this laboratory. Data will be correlated with the mammograms, radiographic and histologic diagnosis and the radiographic patterns of the calcifications. At least 300 calcifications will be analyzed.